Recovery of power during the vaporization of liquefied natural gas is described in U.S. Pat. No. 3,479,832 wherein a single expansion of the circulating multicomponent refrigerant is utilized for power recovery.
An improvement to the patented process was described in a paper entitled "Power Generation from Cryogenic Machinery" presented at the LNG-6 Conference in Tokyo, Japan from Apr. 7 through 10, 1980 and authored by Shigeetsu Miyahara. The improvement involved reducing the number of modules in the main heat exchanger while still relying on a single expander for power recovery.
Examples of processes for recovering energy during the vaporization of liquefied natural gas wherein the heat exchange medium remains in the gaseous phase throughout the entire cycle are shown in U.S. Pat. Nos. 3,293,850 and 3,992,891.
U.S. Pat. Nos. 3,068,659 and 3,183,666 are illustrative of cascade refrigeration systems utilized to vaporize natural gas and recover power by means of expanders.